Thematic Bible: Isaac born to

And Sarah shall conceive, and bring forth to Abraham a son to his old age, at the appointed time which God spake to him. And Abraham shall call the name of his son being born to him, whom Sarah will bear to him, Isaak.

For it has been written, that Abraham had two sons, one by the bondmaid, and one by the free. But he truly of the bondmaid was born according to the flesh; and he of the free through the promise. Which things are spoken figuratively: for these are the two covenants; one truly from mount Sinai, begetting to bondage, which is Agar. read more.
For Agar is mount Sinai in Arabia, and now stands in the same rank With Jerusalem, and is in a servile condition with her children. But Jerusalem above is free, which is mother of us all. For it has been written, Be cheered, O barren, bearing not; break out and cry, she travailing not: for many more the children of the desolate than she having a husband. And we, brethren, as Isaac, are children of promise. But as then he born according to the flesh drove out him according to the Spirit, so also now. But what says the writing? Cast out the bondmaid and her son; for the son of the bondmaid shall not inherit with the son of the free.